Filter Shape Picture ( Re:BITX20A board finished (report JL1KRA)
Hi, All again,toggle quoted messageShow quoted text
Thanks to previous filter discussion around November 7th,2007.
Back to basic, I red W7ZOI article in W1FB's Design Notebook(ARRL).
As recommendation, I replaced C54,55,56 to philips trimmer
as in picture,
I reached C54=82pF, C55=6pF, C56=82pF and changed it to
fixed capacitor. fc=11001000Hz
The ripple in bandpass was minimized less than 3dB.
After this, setting carrier OSC to 109995000Hz,
2-tone injection caribration give me a good result.
Now the both tone are modurated same level.
Still there is some instability the MOS-FETs behaviour
in higher drive level. It's better than before.
The above capacitor value are my case, I am not sure
this will work in other case.
For those who will adjust C54,55,56, I recommend you to
solder these in bootom side of the board. Once these are
soldered between the tall crystals, they are difficult to
JL1KRA Junichi Nakajima
--- In BITX20@..., "qrpjl1kra" <mx6s@...> wrote: